In the production of carbonaceous products such as crude oil and the like, the viscosity of the latter and the condition of the subterranean reservoir in which it is held, often demand that some form of enhancement be utilized. Among the more common forms of enhancement is the injection of steam into the substrate at a sufficient pressure to penetrate the latter and to fluidize the carbonaceous product. The steam also forms a pressurized barrier to drive production fluids in a particular direction toward a producing well or wells.
It is desirable in conducting such a steaming operation, to determine the quality of the steam as it enters the substrate. The latter can normally be at a location any depth along the borehole, well or the like. The determination of steam quality is an economic expedient since the steam will be delivered to the borehole upper end from a source, in a known condition. By the time it flows through the well bore, however, and is in position to enter the substrate, the quality will normally be reduced. Without an accurate determination of quality, it is difficult to estimate the amount of heat being delivered to the substrate.
In brief, what this means is that an oil field steam generator normally produces "wet steam". The steam is not 100% vapor; it contains a liquid phase. Steam quality is a measure of the mass of vapor to the total mass of steam. It is therefore accurate to refer to the vapor phase or the liquid phase of wet steam.
Generally speaking, feed water to a steam generator contains a certain amount of dissolved solids such as salt, i.e. sodium chloride. When the water is turned into wet steam the sodium chloride cannot be contained in the vapor phase; it must be carried in the liquid phase. Therefore the salt content becomes concentrated in the liquid phase.
The higher the steam quality (more vapor phase to liquid phase), the more concentrated the salt content becomes. To measure steam quality, the sodium chloride content of a sample of the liquid phase is ratioed to the sodium chloride content of the feed water. The amount of condensation that occurs does not affect the presently disclosed tool or steam sampler. This tool functions to measure the amount of condensation (i.e. loss of steam quality).
The prior art has disclosed a number of downhole steam samplers which have been successfully utilized. These are used generally for withdrawing a sample of the liquid phase of steam for a steam flow to a well. The sample, when withdrawn from the well, can be analyzed for its chloride ion count as an aid toward establishing an accurate determination of the quality of the steam as it enters the substrate.
In the presently disclosed arrangement, a steam sampler is disclosed which is both durable in structure and relatively simple to operate. The sampler, or tool, is comprised primarily of an elongated casing which is lowered preferably within a lubricator or the like, by a wire line to a particular position or level within a well or borehole. The sampler casing includes an inlet at the upper end for admitting steam at a high pressure and temperature. A discharge opening at the casing lower end directs the pressurized flow into the adjacent subterranean reservoir.
Detent regulated controls maintain the valves in open position and the steam passage unobstructed.
The steam sampler incorporates a fluid separator which permits the liquid phase content to fall by gravity into a container, reservoir or receptacle. The vaporous segment will continue downwardly and be directed from the sampler's discharge opening.
The flow of steam through the elongated casing is regulated by at least one, and preferably by two consecutively positioned flow control valves. Each of said control valves is provided with closure means in the form of a shaft having the detent means. Each said shaft includes a seal member, and preferably a seal member characterized by a metallic seal face, to best mate with a corresponding metal seat formed into the casing.
While a flow of steam passes through the open flow control valves, during a set time period the liquid phase will accumulate in the sampler collecting reservoir. At the end of the set period, flow of steam through the sampler is terminated in a manner to permit the sampler and lubricator to be withdrawn from the well, yet permit continued steam injection into the substrate.
Closure of the flow control valves is triggered by a detent mechanism which functions in conjunction with each valve shaft or shafts. Valve closing is achieved by a physical uplifing of the sampler to a predetermined height, (approximately 10 feet), permitting it to fall, and abruptly halting the fall. The downward momentum and sudden halt will overcome the detent force which retains the respective valve shafts in open position, release of the valve shafts to detents and terminate further steam flow through the fluid separator.
It is therefore an object of the invention to provide a steam sampler of the type contemplated which is responsive to surface induced actuation for closing steam flow control valves.
A further object is to provide a steam sampler which is capable of effective operation in spite of excessively high temperature steam being passed therethrough and which would ordinarily adversely affect internal flow control valves.
A still further object is to provide a steam sampler having metal-to-metal valve seating surfaces which are actuated into engagement with corresponding valve seats to achieve the desired termination of steam flow through the unit.